How do I join 2.75 cast pipe to 3 inch PVC tee?

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by remache74, Sep 11, 2013.

  1. remache74

    remache74 New Member

    Messages:
    5
    Location:
    Miami
    Hello I removed a rusted tee fitting from my sink drain and Im trying to replace it with a PVC TEE. My existing pipe is 2.75" ID and big box stores only sell 3" PVC tee? Any Ideas?
  2. dj2

    dj2 Member

    Messages:
    418
    Location:
    California
    Get no hub couplings (cast iron to PVC). Big box stores may not have a good selection, go to plumbing supply places which sell to the public.
  3. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,351
    Location:
    Yakima WA
    Inside diameter doesn't mean anything here. Pipe size is measured from the outside. Cast iron can have different wall thicknesses, so you must use the actual measurement. You need a special banded coupler to go from the old cast iron to 3" PVC pipe. Then your 3" PVC tee will connect to that. By special, I mean one that will fit your cast iron on one end and 3" PVC on the other. You won't find it at a Big Box store. You need to go to a real plumbing supply house...one where pros buy their materials.
  4. remache74

    remache74 New Member

    Messages:
    5
    Location:
    Miami
    Okay I guess pvc and pipe are measured differently. My pipe is approx 3.25 OD and the pvc is 3.5 OD. So I will try to find a no hub reducer that will work for those numbers. Thanks for the help.
  5. Terry

    Terry Administrator Staff Member

    Messages:
    15,042
    Location:
    Bothell, Washington
    Or you can pick up a copper by cast iron Mission coupling.

    Normally pipes are ID dimension. However the very old cast iron was sized more like copper pipe on the outside.

    [​IMG]
  6. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,680
    Location:
    Cave Creek, Arizona
    It would be an unusual sink drain if it were connected to a 3" pipe.
  7. remache74

    remache74 New Member

    Messages:
    5
    Location:
    Miami
    The tee is 3x3x2...That is the sink drain taps off the tee fitting with approx 2 inch pipe....The tee then goes up to vent and down to drain.
  8. Terry

    Terry Administrator Staff Member

    Messages:
    15,042
    Location:
    Bothell, Washington
    How about a photo 800 pixels or less?
  9. remache74

    remache74 New Member

    Messages:
    5
    Location:
    Miami
    Okay so I called a plumbing store and the lady who answered the phone says I can use a 3 x 3 no hub coupling. Saying that even though the coupling is .25 inch larger than my pipe side that it will compress to fit the pipe once I tighten. Does that sound kosher? Sorry for being a pain with the questions Im an aircraft mechanic thats used to having everthing close tolerance.
  10. Terry

    Terry Administrator Staff Member

    Messages:
    15,042
    Location:
    Bothell, Washington
    No.

    But then she doesn't have to install it and make it work. So she doesn't like how the plumbers do it? My post above gives the right answer. I've been doing this in the field for forty years now.
  11. remache74

    remache74 New Member

    Messages:
    5
    Location:
    Miami
    Like you said copper to pvc no hub worked like a charm. It looks like my pipe was pre 1970 which was before the NPS (national pipe standard) was created. Explaining why my pipe was an odd OD. Thanks for the help.
  12. Hairyhosebib

    Hairyhosebib New Member

    Messages:
    173
    Location:
    Arizona
    You might try going to Ace Hardware. They may carry Febco Fittings. They are an Indiana company that makes rubber fittings for odd sizes of pipes. They will tighten down with big hose clamps.
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